Among “self-identified Democrats and Democratic leaners,” 42 percent preferred Booker, while 20 percent favored Lautenberg. The two men both have high name identification, with 83 percent identifying Lautenberg and 75 percent saying they knew who Booker was.

Booker had much stronger favorability ratings than the incumbent. In the survey, 45 percent viewed Lautenberg favorably, while 66 percent had a favorable impression of Booker.

Democratic Rep. Frank Pallone Jr. was not included in the Senate poll. He is a well-funded possible contender, and his candidacy could could affect support for Booker and Lautenberg.

The Democratic portion of this poll interviewed 336 registered Democratic and Democratic-leaning independent voters and had a 5.4 percent margin of error. It was conducted Jan. 2 to Jan. 6 and included landline and cell phone interviews.